Pump system, method and uses for transporting injection water to an underwater injection well

ABSTRACT

Pump system ( 2 ), method and use for transporting injection water ( 10 ) to an underwater injection well ( 12 ), wherein the pump system ( 2 ) comprises a pressure-tight enclosure ( 14 ) located underwater and containing: —a pump arrangement ( 18 ) for pumping the injection water ( 10 ); —a drive arrangement ( 20 ) connected to the pump arrangement ( 18 ) for operation of the latter; —a cooling arrangement ( 46 ) for removing heat from the interior of the enclosure ( 14 ); and —at least one control unit ( 48 ) for operating control of at least said drive arrangement ( 20 ); wherein the enclosure ( 14 ) also comprises: —an inlet ( 24 ), which is flow-connected to an upstream side of the pump arrangement ( 18 ); and —an outlet ( 28 ), which is flow-connected to a downstream side of the pump arrangement ( 18 ). The characteristic of the pump system ( 2 ) is that the inlet ( 24 ) of the enclosure ( 14 ) is flow-connected to a body of water ( 4 ) in which the enclosure ( 14 ) is located, water from this body of water ( 4 ) being used as injection water ( 10 ) to said underwater injection well ( 12 ); and —the outlet ( 28 ) of the enclosure ( 14 ) is flow-connected to the injection well ( 12 ).

FIELD OF THE INVENTION

The invention relates to a pump system and a method for transportinginjection water to an underwater injection well. The invention alsorelates to the use of the pump system and to the use of said method.

BACKGROUND OF THE INVENTION

A relatively common method for increasing the degree of extraction ofhydrocarbons from an undersea reservoir is to pump water into thereservoir via an underwater injection well, so-called secondaryextraction.

The most common method has been and still is to undertake such offshorewater injection from a surface installation, for example from a mooredplatform or from a floating installation, such a floating installationconsisting of a floating platform or a ship. On such a surfaceinstallation, injection pumps and various other injection-relatedequipment will usually be located above water. Use can thereby be madeof so far well-known, well-tried and effectively functioning surfaceequipment, including known injection pumps and their drive arrangements,for such injection purposes. The major disadvantage with water injectionfrom such a surface installation, however, is the scope, complexity andthe associated costs of constructing and installing the surfaceinstallation offshore. Such surface installations are therefore largelyused in connection with hydrocarbon extraction from large oil fields.

As underwater completion and underwater production have become morecommon, it has also become more common to inject water by means ofunderwater equipment located on or near a seabed, for example on thebottom of an ocean or lake. In this context, the injection water mayalso be subjected to various treatment underwater, for example filteringand/or chemical treatment, by means of associated equipment located onor near the seabed. The use of such underwater equipment is typicallyundertaken in connection with secondary extraction from smaller and/orcomplex oil fields, and/or in secondary extraction at greater waterdepths than is usual for surface installations. In the case ofunderwater completion, the well head of the injection well is located onthe seabed, and said underwater equipment is flow-connected to the wellhead. This underwater equipment comprises at least an underwaterinjection pump, which will typically be specially adapted for operationunderwater at the relevant water depth. For this reason, such anunderwater injection pump will typically be of a design which,technically speaking, is substantially more complex, more extensive andmore robust, and thereby substantially more costly than a correspondingwell-known, well-tried and effectively functioning surface pump. Inaddition, such an underwater injection pump is often exposed to verydemanding and harsh operating conditions underwater. Such operatingconditions often reduce the operating reliability and service life ofthe underwater pump. This may therefore lead to shorter maintenanceintervals and thereby more frequent intervention operations, andincreased operating costs associated with operation of the underwaterpump. In the worst case, such operating conditions and associateddisadvantages may render seabed-based water injection into an injectionwell impossible.

It is thus desirable to avoid the use of such specially adapted, costlyand sometimes unreliable underwater injection pumps for injecting waterinto an underwater-completed injection well. It is desirable to make thewater injection more cost effective and reduce service intervals.

STATE OF THE ART

US 2008/0190291 A1 describes, in the form of a method and an apparatus,a submersible processing environment for diverse underwater processingof a hydrocarbon stream that is produced from an underwater well.

The submersible processing environment according to US 2008/0190291 A1,is used for the processing of a hydrocarbon stream from an underwaterwell.

In view of the prior art, there is a need to provide more cost efficientand reliable water injection equipment. There is a further need toprovide a technical solution in which such equipment can be arranged ona deck of a floating vessel, and then be submerged in a body of waterthrough a working aperture (“moon pool”) in the deck of the vessel. Itis also desirable, at a later date, to retrieve the equipment via such aworking aperture in the deck of the vessel, for example for maintenanceand/or repair of the equipment, possibly for the replacement of variouscomponents etc.

SUMMARY

It is an object of the invention to remedy or to reduce at least onedisadvantage of the state of the art, or at least to provide a usefulalternative to the state of the art.

This object is achieved by the features of the independent claims. Thedependent claims describe embodiments of the invention.

According to a first aspect of the invention, a pump system is providedfor transporting injection water to an underwater injection well,wherein the pump system comprises a pressure-tight enclosure locatedunderwater and containing:

-   -   a pump arrangement for pumping the injection water;    -   a drive arrangement connected to the pump arrangement for        operation of the latter;    -   a cooling arrangement for removing heat from the interior of the        enclosure; and    -   at least one control unit for operating control of at least said        drive arrangement;        wherein the enclosure also comprises:    -   an inlet which is flow-connected to an upstream side of the pump        arrangement; and    -   an outlet which is flow-connected to a downstream side of the        pump arrangement. In the pump system, the inlet of the enclosure        is flow-connected to a body of water in which the enclosure is        located, water from this body of water being used as injection        water to said underwater injection well; and    -   the outlet of the enclosure is flow-connected to the injection        well.

Using such a submerged pump system, it is possible for so farwell-known, well-tried, effectively functioning and reliable surfacepumps, and drive arrangements for these, to be located underwater insaid body of water. Untreated water can then be drawn in more or lessdirectly from the surrounding body of water, to be then pumped onwardsdown into the underwater-completed injection well. This avoids having touse specially adapted, costly and complicated underwater equipment forsuch water injection purposes.

The pump system in question might therefore represent a substantialtechnical contribution in being able to undertake economically viable,secondary extraction from smaller and/or complex oil fields, and fromoil fields at greater water depths than is usual for surfaceinstallations.

In an embodiment, at least one control unit of the pump system maycomprise various electronic components, including electronic circuitboards, programs, transmitter units, receiver units, circuit breakers,couplings, power connections and the like, for controlling and possiblymonitoring the operation of the pump system when installed in itsposition of use underwater. The scope of the components in the controlunit is determined by the actual design of the pump system. The controlunit may therefore at least comprise components/equipment enabling it tocommunicate signals with said drive arrangement, and possibly also withsaid cooling arrangement and/or other equipment in the pump system.

The pump system may also comprise various coupling equipment, forexample valves, couplings, flanges, packings, connecting lines andhoses, for connecting various components which are included in or whichare associated with the pressure-tight enclosure.

The pump system may furthermore comprise various regulating equipmentfor regulating and thereby controlling the operation of variouscomponents in the pump system.

In addition, the pump system may be designed for connection to variousauxiliary equipment, which among other things is used to carry outservicing operations on the pump system, or on equipment which isassociated with the pump system, possibly for coupling various equipmentto the pump system. Such auxiliary equipment may therefore includeROV-based equipment, where an unmanned and remotely controlledunderwater vessel (“ROV”) carries out the relevant servicing operationsby means of remote control from a host vessel on the surface. In thelatter case the equipment in question, which is connected to the pumpsystem, must also be designed for interaction with the ROV-basedequipment.

Said enclosure in the pump system may advantageously be located on ornear the bottom of a body of water, for example on a seabed or on thebed of a lake, river or delta. In this context, the enclosure maypossibly be located on a suitable foundation.

Furthermore, the pump arrangement in the enclosure may comprise orconsist of any suitable pump arrangement, for example a centrifugalpump. In addition, the drive arrangement of the pump arrangement maycomprise or consist of any suitable drive arrangement, for example anelectric motor or a hydraulic motor.

The pressure-tight enclosure of the pump system may also contain alubrication arrangement for lubricating at least one moving part in thepump arrangement or the drive arrangement.

In addition or alternatively, if the pump arrangement and/or the drivearrangement comprise rotating parts, the pump arrangement and/or thedrive arrangement may be provided with magnetic bearings for theoperating support of at least one rotating part in the pump arrangementand/or in the drive arrangement. In this context, the magnetic bearingsmay be connected to at least one control unit for operating control ofthe bearings. The magnetic bearings may also be connected to at leastone source (e.g. electric power source) for supplying drive power to thebearings.

The pressure-tight enclosure may also contain monitoring equipment foroperational monitoring of at least said pump arrangement, drivearrangement and cooling arrangement. In this context, the monitoringequipment is connected to at least one said control unit for operatingcontrol of the monitoring equipment and the transmission of monitoringdata to a remote host device. The monitoring equipment is also connectedto at least one source (e.g. electric power source) for supplying drivepower to the monitoring equipment.

Furthermore, the pressure-tight enclosure may contain a gas, for exampleair, at atmospheric or virtually atmospheric pressure, that is to say aninternal pressure of approximately 1 atmosphere. The pressure inside theenclosure may for example lie within a range of about 1 to about 2 bar.This assumes that the enclosure is designed to be capable ofwithstanding pressure differences between the water pressure thatprevails outside the enclosure at the water depth in question, and theatmospheric or virtually atmospheric pressure inside the enclosure. Setto such an internal gas pressure, the enclosure can be raised to thesurface and opened for servicing, modification or the like, withoutdangerous situations arising as a result of a pressure differencebetween the interior of the enclosure and the surrounding atmosphericpressure at the surface. If desired or necessary, the gas in theenclosure may also consist of an inert gas, for example nitrogen orargon. This may provide improved electric isolation and/or reducecorrosion.

In addition, the enclosure may be connected via a cabled connection to aremote host device for transferring contaminated gas from the enclosureand for returning uncontaminated gas to the enclosure. Such a solutionmay be appropriate, for example, if it is desirable to remove watervapor from the injection water and/or vapor for a coolant and/or a fluidlubricant, for example oil vapor, from the interior of the enclosure.The contaminated gas can thereby be transported from the enclosure andto the host device, where the contaminated gas is either cleaned orreplaced. The uncontaminated gas may then be returned to the enclosurevia the cabled connection.

In addition, equipment, modules and units that are to be locatedunderwater offshore can often be large, heavy and bulky, possibly with arelatively large lateral extent. For this reason, it may be difficult tolocate such equipment on a deck of a floating vessel, for example aboat, for transport from the shore to the relevant location offshore. Ifthe vessel is also provided with a working aperture (“moon pool”) in thedeck of the vessel, it may also be difficult to lower such equipmentdown through the working aperture in the deck, and possibly also toretrieve the equipment though this working aperture. In some cases,therefore, bulky equipment must be transported suspended under or behindthe vessel during transport offshore.

Such transport of awkward equipment is shown, for example, in thepublication WO 03/074353 A1, which corresponds to NO 316168 B1, and inpublication WO 2009/070034 A2. Alternatively, such equipment may belocated on a deck of a large transport vessel, for example a lighter,and transported to the relevant location offshore. The equipment is thenhoisted over the side of the vessel and lowered down into the water.Such a working operation may also be awkward with an associateduncertainty and risk.

Since the enclosure in the pump system in question may also be large,heavy and bulky, the pump arrangement and drive arrangement of theenclosure may advantageously be vertically aligned in relation to oneanother. Furthermore, the enclosure may be designed with an outerperimeter or circumference that fits inside or is specially adapted tosuch a working aperture in a deck of a floating vessel. In this context,and by means of suitable aids, the vessel is designed to be capable oflowering the enclosure down into the water, and where necessaryretrieving the enclosure from the water through the working aperture inthe deck of the vessel. It is thereby possible to transport theenclosure and its contents on the deck of the vessel when shipping theenclosure out to the relevant location offshore, following which theenclosure is lowered down into the water via said working aperture inthe deck of the vessel.

Aligning the pump arrangement and its drive arrangement vertically inrelation to one another affords a relatively narrow enclosure, whichfits both on the deck of the vessel and inside the working aperture inthe deck. For this reason the enclosure can advantageously have a heightthat is greater than the largest horizontal transverse dimension of theenclosure. The enclosure may for example comprise or consist of avertically upright, cylindrical container of a height that is greaterthan the diameter of the container. In this context, the pumparrangement can be arranged vertically beneath the drive arrangement, orthe pump arrangement can be arranged vertically above the drivearrangement.

In one embodiment, said control unit may comprise at least one remotelycontrolled control unit, which, via a cabled connection, is connected toa remote host device for transmitting at least control signals to thecontrol unit. Such a cabled connection may consist, for example, of acontrol cable (“umbilical line”).

Alternatively or in addition, the enclosure may be connected via acabled connection to a remote host device for transmitting drive powerto powered equipment in the pump system. Such a cabled connection mayconsist, for example, of a suitable power transmission cable.

In another embodiment, the enclosure may be connected via a cabledconnection to a remote host device for transmitting both control signalsto the control unit and drive power to powered equipment in the pumpsystem.

In addition, said control system may also comprise at least one remotelycontrolled backup control unit, which is connected via a wirelessconnection to a remote host device for transmitting at least controlsignals to the control unit. In this context, the backup control unit isconnected to a transceiver for wireless communication with the remotehost device. The wireless connection may consist, for example, of anacoustic connection or a radio frequency connection. Alternatively or inaddition, the enclosure may be provided with a power supply foroperation of the remotely controlled backup control unit. Said powersupply may consist, for example, of at least one battery.

Furthermore, the cooling arrangement of the enclosure may comprise atleast one closed flow circuit, for example a pipe loop, containing acoolant, where the closed flow circuit is connected to the internalatmosphere of the enclosure for absorbing heat therefrom, and where theclosed flow circuit comprises a heat exchanger, which is connected tosaid body of water on the outside of the enclosure for removing heattransmitted from the internal atmosphere of the enclosure by way of thecoolant of the flow circuit. This cooling arrangement also comprises ameans of delivery for the coolant, for example a suitable pump. The heatexchanger may advantageously be arranged on the outside of the enclosureand may therefore be in direct contact with the cooling body of water.Alternatively, the heat exchanger may be arranged inside the enclosureand may comprise an open flow circuit, which via at least oneliquid-tight bushing through the wall of the enclosure is in directcontact with the cooling body of water outside the enclosure.

Alternatively, the cooling arrangement of the enclosure may comprise anopen flow circuit, for example a pipe connection/hose connection,including a control cable (“umbilical line”), containing a coolant,where the open flow circuit is connected to the internal atmosphere ofthe enclosure for absorbing heat therefrom, and where the open flowcircuit is connected to a remote host device for at least thecirculation and possibly also the replenishing of coolant, and forremoving heat transmitted from the internal atmosphere of the enclosureby means of the coolant of the flow circuit.

Furthermore, the lubrication arrangement of the enclosure may compriseat least one closed flow circuit, for example a pipe loop, containing afluid lubricant, where the closed flow circuit is connected tolubricated equipment in the pump system. This lubrication arrangementalso comprises a means of delivery for the fluid lubricant, for examplea suitable pump.

Alternatively, the lubrication arrangement of the enclosure may comprisean open flow circuit, for example a pipe connection/hose connection,including a control cable (“umbilical line”), containing a fluidlubricant, where the open flow circuit is connected to lubricatedequipment in the pump system, and where the open flow circuit isconnected to a remote host device for at least the circulation andpossibly also the replenishing of fluid lubricant, and for lubricatingthe lubricated equipment in the pump system.

For transmitting at least control signals to the control unit, saidcontrol unit may be connected to at least one wet-mateable plugconnection arranged in the wall of the enclosure and designed forcoupling to a separate, cabled connection.

Alternatively or in addition, and for transmitting drive power to thepowered equipment in the pump system, the wall of the enclosure may beprovided with at least one wet-mateable plug connection designed forcoupling to a separate, cabled connection.

As a further alternative or in addition, and for transmitting bothcontrol signals to the control unit and drive power to powered equipmentin the pump system, the wall of the enclosure may be provided with atleast one wet-mateable plug connection designed for coupling to aseparate, cabled connection.

All of these plug connections may for example comprise or consist of aplug and a socket, which afford a mating fit when coupled together.

By means of such a wet-mateable plug connection, a cabled connection,for example a control cable and/or a power transmission cable, can beeasily coupled to or uncoupled from the enclosure by means, for example,of a remotely controlled underwater vessel (“ROV”).

Said remote host device, moreover, may comprise or consist of a surfaceinstallation on land or offshore. On land the surface installation maycomprise, for example, of a building or the like, in which an operatorof the pump system is situated. Offshore the surface installation maycomprise or consist of an anchored platform or a floating installation,for example a floating platform or a suitable vessel/ship.

The inlet of the enclosure may furthermore be designed to be closeable,for example by means of a suitable valve arrangement.

Alternatively or in addition, the outlet of the enclosure may bedesigned to be closeable, for example by means of a suitable valvearrangement. In one embodiment the outlet of the enclosure may beconnected to the injection well via an underwater line, for example apipeline. In another embodiment, the outlet of the enclosure may bedirectly connected to the injection well, for example the outlet isconnected to a well head for the injection well.

In addition, the enclosure may be flow-connected to at least oneunderwater installation for treatment of the injection water, where saidunderwater installation is located underwater in said body of water. Theenclosure can therefore be connected to said underwater installation viaan underwater line, for example a pipeline.

Said underwater installation may comprise at least one arrangement forremoving solid particles from the injection water without filtering. Inthis context it is most advantageous if the inlet of the enclosure isconnected to one or more such arrangements. At least some solidparticles will thereby be removed from the injection water before thisreaches the enclosure and its pump arrangement. An example of such anunderwater arrangement is described in WO 2007/035106 A1, which isincorporated herein by reference in its entirety. This underwaterarrangement comprises a closed chamber, which is designed to allow thefeed water to be fed directly into a lower part of the closed chamber,and which is also designed to allow the treated water to be fed out ofan upper part of the closed chamber. This closed chamber also has across sectional area which is designed to allow the water to flow fromthe lower part to the upper part with a rate of flow that is low enoughfor the unwanted solid particles to be precipitated out of the waterunder gravity. The closed chamber may furthermore be designed as acontainer or module that is located on a seabed or the like, forexample.

Alternatively or in addition, said underwater installation may compriseat least one arrangement for chemical treatment of the injection water.In this context, at least one inlet and outlet of the enclosure may beflow-connected to one or more such arrangements for chemical treatmentof the injection water. An example of such a chemical treatmentarrangement is described in WO 2004/090284 A1, which is incorporatedherein by reference in its entirety. This patent publication relates toa method and an apparatus for undersea chemical treatment of injectionwater, using a modular underwater apparatus that is connected to aninjection well for injection of the water. The apparatus comprises atleast one container, which is provided with at least one type ofwater-soluble solid chemical. The container can be changed, for example,by means of a remotely controlled underwater vessel (“ROV”). The wateris then brought into contact with the solid chemical, in such a way thatit is gradually dissolved and mixed with the water. The ready-treatedwater is then injected into a reservoir connected to the well. Chemicaltreatment and water injection can thereby be undertaken without havingto use a directly superjacent surface installation or vessel. Thewater-soluble solid chemical may comprise chlorine and/or biocide, butalso various other chemicals, such as said oxygen-removal agents,corrosion inhibitors and settlement inhibitors. This chemical treatmentarrangement may consist of a separate unit or it may be incorporatedinto the aforesaid underwater arrangement for the removal of unwantedsolid particles from the feed water without filtering.

As a further alternative or in addition, said underwater installationmay comprise at least one arrangement for the destruction of organicmaterial in the injection water. In this context also, at least oneinlet and outlet of the enclosure may be flow-connected to one or moresuch arrangements for the destruction of organic material in theinjection water. An example of such a destructive arrangement isdescribed in WO 2007/073198 A1, which is incorporated herein byreference in its entirety. This patent publication relates to a methodand an arrangement for destroying organic material in injection waterfor an injection well. The arrangement uses at least one electrochemicalcell with associated operating means for the in situ electrolyticproduction from water of at least short-lived, free hydroxyl radicals.With the aid of the operating means, the electrochemical cell isdesigned to be capable of ducting the injection water through it asbasic material for the in situ production of at least said free hydroxylradicals from the injection water. Such free hydroxyl radicals willimmediately destroy organic material with which they come into contactin the injection water. This destructive arrangement may consist of aseparate unit or it may be incorporated into the aforesaid underwaterarrangement for the removal of unwanted solid particles from the feedwater without filtering. As a further alternative, the destructivearrangement may be combined with the aforementioned chemical treatmentarrangement.

At least said one underwater installation for treatment of the injectionwater may, like the enclosure, advantageously be located on or near thebottom of a body of water, for example on a seabed or on the bed of alake, river or delta. In this context, the underwater installation may,if necessary, be located on a suitable foundation.

According to a second aspect of the invention, a method is provided fortransporting injection water to an underwater injection well, where themethod uses a pump system comprising a pressure-tight enclosure whichcontains:

-   -   a pump arrangement for pumping the injection water;    -   a drive arrangement connected to the pump arrangement for        operation of the latter;    -   a cooling arrangement for removing heat from the interior of the        enclosure; and    -   at least one control unit for operating control of at least said        drive arrangement;        where the enclosure also comprises:    -   an inlet which is flow-connected to an upstream side of the pump        arrangement; and    -   an outlet which is flow-connected to a downstream side of the        pump arrangement;        where the method comprises the following steps:

(A) lowering the pressure-tight enclosure down into the water andlocating the enclosure underwater.

The characteristic of the method is that it also comprises the followingsteps:

(B) flow-connecting the inlet of the enclosure to a body of water inwhich the enclosure is located, water from this body of water being usedas injection water to said underwater injection well;

(C) flow-connecting the outlet of the enclosure to the injection well;and

(D) starting said drive arrangement and thereby the pump arrangement inorder thus to pump the injection water onwards to the injection well.

The same comments as were made in connection with the precedingdescription of the pump system according to the first aspect of theinvention also apply to the method in question according to this secondaspect of the invention.

In the embodiments, method may also comprise the following steps:

-   -   aligning the pump arrangement and the drive arrangement        vertically in relation to one another;    -   designing the enclosure with an outer perimeter (circumference)        that fits inside a working aperture (“moon pool”) in a deck of a        floating vessel; and    -   lowering the enclosure down into the water via the working        aperture in the deck of the vessel.

The enclosure and its contents, which may be large, heavy and bulky, canthereby be transported on the deck of a vessel when shipping theenclosure out to a location offshore, following which the enclosure islowered down into the water via a working aperture (“moon pool”) in thedeck of the vessel. At a later date the enclosure can thereby beretrieved from the water via this working aperture. Aligning the pumparrangement and its drive arrangement vertically in relation to oneanother affords a relatively narrow enclosure, which fits both on thedeck of the vessel and inside the working aperture in the deck. Thisobviates the need, for example, to transport such an enclosure withcontents suspended beneath or behind the vessel when it is transportedoffshore, and possibly hoisting the equipment over the side of a vesselbefore lowering the equipment down into the water.

Furthermore, the method may also comprise the following steps:

-   -   locating at least one underwater installation for treatment of        the injection water underwater in said body of water; and    -   flow-connecting the enclosure to said underwater installation        for treatment of the injection water.

As stated in connection with the first aspect of the invention, saidunderwater installation may comprise at least one of the following typesof underwater installations:

-   -   an arrangement for removing solid particles from the injection        water without filtering, as described, for example, in WO        2007/035106 A1;    -   an arrangement for chemical treatment of the injection water, as        described, for example, in WO 2004/090284 A1; and    -   an arrangement for the destruction of organic material in the        injection water, as described, for example, in WO 2007/073198        A1.

According to a third aspect of the invention, the use of a pump systemaccording to the first aspect of the invention is for transportinginjection water to an underwater injection well.

According to a fourth aspect of the invention, the use of a methodaccording to the second aspect of the invention is for transportinginjection water to an underwater injection well.

The features of the embodiments described above and further below can becombined with each other unless noted to the contrary. Any of thedescribed configurations of the pump system may be employed within themethod of the second aspect of the invention, and the pump system may beconfigured so as to be capable of being employed or of implementing anyof the method steps described above and further below.

BRIEF DESCRIPTION OF DRAWINGS

Some non-limiting examples of embodiments according to the invention aredescribed below with reference to the accompanying drawing, in which

FIG. 1 shows a highly schematic vertical plan view, partly in section,of a pump system according to an embodiment of the invention,comprising, among other things, a pressure-tight enclosure, whichcontains a pump arrangement, etc., where the enclosure is locatedunderwater on a seabed, and the enclosure is flow-connected to, amongother things, a remote underwater injection well;

FIG. 2, also highly schematic and to a smaller scale, shows a firstembodiment of a pump system in question, comprising the enclosureaccording to FIG. 1, where the upstream side of the enclosure isflow-connected to an underwater installation for treatment of theinjection water that is drawn directly from the sea which surrounds theenclosure and the underwater installation, and where both the enclosureand the underwater installation are each connected to a remote andfloating platform offshore for transmitting various signals, includingcontrol signals and monitoring data, and drive power to poweredequipment in the enclosure and the underwater installation; and

FIG. 3, also highly schematic, shows a second embodiment of a pumpsystem in question and the underwater installation according to FIG. 2,where, however, both the enclosure and the underwater installation areeach connected to a remote location offshore or on land for transmittingsaid signals and drive power to the enclosure and the underwaterinstallation.

The figures, as stated, are highly schematic and show only parts andequipment for the purpose of a better understanding of the invention.Furthermore, the figures are highly distorted with regard to therelative dimensions of parts and components shown in the figures i.e.the objects are not to scale with each other. In addition, the figuresare highly simplified with regard to the shape and amount of detail ofsuch parts and components. Identical, equivalent or corresponding partsin the figures have largely been quoted below with the same referencenumerals.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 1 shows a pump system 2 according to an embodiment of the inventionlocated in a body of water in the form of seawater 4, where the pumpsystem 2 is situated on a seabed 6 beneath a sea surface 8 (shown onlyin FIGS. 2 and 3). The pump system is designed for transportinginjection water 10 to a remote injection well 12 on the seabed 6 (seeFIGS. 2 and 3). In this context, seawater 4 is used as untreated waterfor the injection water 10 to the injection well 12.

The injection water can consist of water/untreated water that is drawnfrom a body of water in which the pump system in question is locatedwhen the system is in its position of use underwater. This body of watermay consist of salt seawater, for example, or, when installed at adifferent location, of water from a lake, river, spring or groundwaterdeposit.

The pump system in question can furthermore be controlled and possiblymonitored from a remote host device via one or more cabled and/orwireless communications connections. The pump system may also besupplied with power from a remote host device via at least one cabledpower transmission connection. Such a host device may include a surfaceinstallation on land or offshore. Alternatively or in addition, the pumpsystem in question may be linked to one or more underwater installationsfor various treatment of the injection water, for example filteringand/or various chemical treatment of the injection water.

The pump system 2 comprises a pressure-tight enclosure 14, which islocated on a foundation 16 on the seabed 6. In this embodiment, theenclosure 14 consists of a vertically upright, cylindrical container ofa height which is greater than the diameter of the container. Theenclosure 14 contains an inert gas 17, for example nitrogen or argon,which is set to an atmospheric or virtually atmospheric pressure. Theenclosure 14 also contains a pump arrangement for pumping the injectionwater 10, and a drive arrangement connected to the pump arrangement foroperating the latter. In this embodiment, the pump arrangement is of acentrifugal pump 18, whilst the drive arrangement comprises an electricmotor 20, which is rotatably connected to the centrifugal pump 18 via arotatable shaft 22. In this connection, the centrifugal pump 18 and theelectric motor 20 are vertically aligned in relation to one another, andthe centrifugal pump 18 is arranged vertically below the electric motor20.

The enclosure 14 further comprises an inlet in the form of an external,first flange coupling 24, which via a first connecting pipe 26 isflow-connected to an upstream side of the centrifugal pump 18. Theenclosure 14 also comprises an outlet in the form of an external, secondflange coupling 28, which via a second connecting pipe 30 isflow-connected to a downstream side of the centrifugal pump 18. Theinlet and outlet of the enclosure 14 are also of closeable design, inthat the first flange coupling 24 is coupled to a first valve 32, whilstthe second flange coupling 28 is coupled to a second valve 34.Furthermore, the valves 32, 34 can be opened or closed via associatedactuator arrangements (not shown), which are connected to and driven andcontrolled by a remotely controlled control unit 48 in the enclosure 14.Alternatively, the valves 32, 34 may be opened or closed by means of aremotely controlled underwater vessel (“ROV”).

Each valve 32, 34 is also flow-connected to an injection pipeline 36 fortransporting the injection water 10. An upstream end of the injectionpipeline 36 is connected to an underwater installation 38 located on theseabed 6 and is designed for various treatment of the seawater 4, whilsta downstream end of the injection pipeline 36 is connected to a wellhead 40 coupled to said injection well 12 on the seabed 6 (see FIGS. 2and 3). The seawater 4 surrounding the underwater installation 38 isused as untreated water for the injection water 10. The untreated wateris drawn from a layer of water situated just above the seabed 6, and isintroduced into the underwater installation 38 via an intake pipe 42coupled thereto. The intake pipe 42 may also be provided with orconnected to one or more suitable intake filters.

The enclosure 14 further contains a lubrication arrangement forlubricating various moving parts in the centrifugal pump 18 and theelectric motor 20. The enclosure 14 moreover contains a coolingarrangement for removing heat that is generated by equipment inside theenclosure 14 when in operation. The enclosure 14 then also contains saidremotely controlled control unit 48, which in addition to controllingsaid valves 32, 34 is designed for operating control of, among otherthings, the electric motor 20 and said lubrication arrangement andcooling arrangement. In this embodiment, the lubrication arrangement,the cooling arrangement and the control unit comprise respective units(or modules), which are vertically aligned in relation to one another,and which are also arranged side by side with the centrifugal pump 18and the electric motor 20 (see FIG. 1). The enclosure 14 thereforecontains a lower lubrication unit 44, a middle cooling unit 46 and anupper, remotely controlled control unit 48, which has already beenmentioned in connection with control of said valves 32, 34. By aligningsaid equipment 18, 20, 44, 46, 48 vertically inside the verticallyupright, cylindrical and relatively narrow enclosure 14 it is alsopossible to design the enclosure 14 with an outer circumference whichfits inside a working aperture (“moon pool”) in a deck of a floatingvessel (not shown). The enclosure 14 and its contents can thereby betransported on the deck of the vessel when shipping out to the relevantoffshore location, following which the enclosure 14 can be lowered downinto the seawater 4, and if necessary also retrieved from the seawater 4via the working aperture in the deck of the vessel.

The lower lubrication unit 44 contains, among other things, a fluidlubricant (not shown) and a suitable pump (not shown) for the lubricant.Drive power and control signals to the lubricant pump are transmittedfrom the upper control unit 48 via a first connecting line 50. Saidlubrication arrangement also comprises a first lubricant pipe loop 52and a second lubricant pipe loop 54, which connect the lubrication unit44 to lubricated components of the centrifugal pump 18 and the electricmotor 20 respectively. In operation, the lubrication unit 44 is therebycapable of supplying such components with fluid lubricant. The directionof flow of the lubricant is moreover indicated by black arrows in FIG.1.

The middle cooling unit 46 furthermore contains, among other things, asuitable coolant (not shown) and a suitable compressor/pump (not shown)for the coolant. Drive power and control signals to the coolant pump aretransmitted from the upper control unit 48 via a second connecting line56. Said cooling arrangement also comprises a coolant pipe loop 58,which via liquid-tight bushings (not shown) through the wall of theenclosure 14 connect the cooling unit 46 to a heat exchanger 60 arrangedon the outside of the enclosure 14. In operation, the cooling unit 46 isthereby able to absorb heat that is generated by equipment inside theenclosure 14 and to transmit this heat to the heat exchanger 60 on theoutside of the enclosure 14. The heat exchanger 60 exchanges thetransmitted heat with colder seawater 4, which surrounds the enclosure14. A cooled coolant can thereby be returned to the cooling unit 46 forfresh absorption of heat generated in the enclosure 14. The direction offlow of the coolant is also indicated by black arrows in FIG. 1.

In this embodiment, the enclosure 14 also contains various monitoringequipment (not shown), for example one or more cameras, associated lightsources, various detectors including gas detectors, for operationalmonitoring of the centrifugal pump 18, the electric motor 20 and saidcooling arrangement and lubrication arrangement. Drive power, controlsignals and monitoring data to/from such monitoring equipment are alsotransmitted from/to the upper control unit 48.

The upper, remotely controlled control unit 48 furthermore containsvarious electronic components and equipment to the extent necessary inorder to achieve the required functionality of the pump system 2 inquestion. The control unit 48 may therefore contain various electronicprocessors and circuit boards, data programs, electronic circuitbreakers and couplings, but also various data communications equipment,including transceivers and signal converters, and any smaller energysources for the operation, control and/or signal transmission to/fromvarious equipment and components in the enclosure 14, for example one ormore batteries for the operation of monitoring equipment in theenclosure 14. The equipment is as such generally known, however, andwill therefore not be discussed in more detail here. The control unit 48also transmits control signals to the electric motor 20 via a thirdconnecting line 62.

The wall of an upper part of the enclosure 14 is moreover provided witha releasable and wet-mateable plug connection 64 of the plug 64 a andsocket 64 b type. The socket 64 b is situated on the outside of theenclosure 14 and is connected to a liquid-tight bushing (not shown)through the wall of the enclosure 14, whilst the plug 64 a is coupled toa separate control cable (“umbilical line”) 66, which is connected to aremote host device. The plug 64 a can thereby be coupled to or uncoupledfrom the socket 64 b by means, for example of an unmanned and remotelycontrolled underwater vessel (“ROV”). The control cable 66 is furtherdesigned to be capable of transmitting control signals and monitoringdata between the host device and the control unit 48, and designed to becapable of transmitting drive power from the host device to poweredequipment in the pump system 2. The control cable 66 thereforeconstitutes both a signal transmission cable and a power transmissioncable. Since the electric motor 20 requires a lot of electrical drivepower, a power transmission cable 68 is arranged between the electricmotor 20 and a power outlet (not shown) in the socket 64 b. A fourthconnecting line 70 is also arranged between the socket 64 b and theupper control unit 48 for transmitting control signals, monitoring dataand any drive power between the remote host device and the control unit48.

FIG. 2 shows an embodiment in which the control cable 66 is connected toa remote host device in the form of a floating platform 72 situatedoffshore. FIG. 3 shows another embodiment in which the control cable 66is connected to a remote surface installation on land (not shown).

As stated, FIGS. 2 and 3 also show that the upstream end of theinjection pipeline 36 is connected to said underwater installation 38,which is located on the seabed 6 for various treatment of the untreatedinjection water, that is to say the seawater 4, which surrounds theunderwater installation 38. The seawater 4 is drawn from a layer ofwater situated just above the seabed 6 and is introduced into theunderwater installation 38 via its intake pipe 42. This underwaterinstallation 38 comprises, among other things, at least one arrangement(not shown) for removing solid particles from the seawater 4 withoutfiltering. An example of such an underwater arrangement is described insaid WO 2007/035106 A1, in which solid particles are precipitated out ofthe seawater 4 under gravity, so-called sedimentation.

In addition, the underwater installation 38 may comprise at least onearrangement (not shown) for chemical treatment of the water which runsout from the first aforementioned arrangement for the sedimentation ofsolid particles. The water running out is brought into contact with atleast one type of water-soluble solid chemical for gradually dissolvingand mixing with the water. Such water-soluble solid chemicals mayconsist of chlorine, biocide, oxygen-removal agents, corrosioninhibitors and/or settlement inhibitors. An example of such a chemicaltreatment arrangement is described in the aforementioned WO 2004/090284A1. In this embodiment, the underwater installation 38 comprises adischarge point for the injection water 10. Following said watertreatment in the underwater installation 38 and with the aid of thecentrifugal pump 18 in the enclosure 14, the treated injection water 10is pumped through said underwater pipeline 36 and onwards to the wellhead 40 of the injection well 12. The injection water 10 is then pumpeddown into the injection well 12 and into an underground oil reservoir 74in a subsurface 76 for the secondary extraction of crude oil therefrom.The direction of flow of the injection water 10 is indicated by blackarrows in all figures.

FIG. 2 also shows that the underwater installation 38 is connected tothe floating platform 72 via a further control cable (“umbilical line”)for transmitting control signals, drive power and/or monitoring signals.FIG. 3, on the other hand, shows that the further control cable 78 isconnected to said remote surface installation on land (not shown).

Note that the features of the above embodiments can be combined, andthat the pump system 2 of FIGS. 2 and 3 may be configured as describedwith respect to FIG. 1.

1. A pump system (2) for transporting injection water (10) to anunderwater injection well (12), where the pump system (2) comprises apressure-tight enclosure (14) located underwater and containing: a pumparrangement (18) for pumping the injection water (10); a drivearrangement (20) connected to the pump arrangement (18) for operation ofthe latter; a cooling arrangement (46) for removing heat from theinterior of the enclosure (14); and at least one control unit (48) foroperating control of at least said drive arrangement (20); where theenclosure (14) also comprises: an inlet (24) which is flow-connected toan upstream side of the pump arrangement (18); and an outlet (28) whichis flow-connected to a downstream side of the pump arrangement (18),characterized in that the inlet (24) of the enclosure (14) isflow-connected to a body of water (4), in which the enclosure (14) islocated, water from this body of water (4) being used as injection water(10) to said underwater injection well (12); and the outlet (28) of theenclosure (14) is flow-connected to the injection well (12).
 2. The pumpsystem (2) as claimed in claim 1, characterized in that thepressure-tight enclosure (14) contains a lubrication arrangement (44)for lubricating at least one moving part in the pump arrangement (18)and the drive arrangement (20).
 3. The pump system (2) as claimed inclaim 1, characterized in that the pump arrangement (18) and the drivearrangement (20) are provided with magnetic bearings for the operatingsupport of at least one rotating part in the pump arrangement (18) andthe drive arrangement (20); the magnetic bearings are connected to atleast one control unit (48) for operating control of the bearings; andthe magnetic bearings are connected to at least one source for supplyingdrive power to the bearings.
 4. The pump system (2) as claimed in claim1, characterized in that the pressure-tight enclosure (14) containsmonitoring equipment for operational monitoring of at least said pumparrangement (18), drive arrangement (20) and cooling arrangement (46);the monitoring equipment is connected to at least one said control unit(48) for operating control of the monitoring equipment and thetransmission of monitoring data to a remote host device (72); and themonitoring equipment is also connected to at least one source forsupplying drive power to the monitoring equipment.
 5. The pump system(2) as claimed in claim 1, characterized in that the pressure-tightenclosure (14) contains a gas (17) at atmospheric or virtuallyatmospheric pressure, preferably at a pressure between about 1 bar andabout 2 bar.
 6. The pump system (2) as claimed in claim 5, characterizedin that the enclosure (14) is connected via a cabled connection (66) toa remote host device (72) for transferring contaminated gas (17) fromthe enclosure (14) and for returning uncontaminated gas (17) to theenclosure (14).
 7. The pump system (2) as claimed in claim 1,characterized in that the pump arrangement (18) and drive arrangement(20) are vertically aligned in relation to one another.
 8. The pumpsystem (2) as claimed in claim 7, characterized in that the drivearrangement (20) is mounted vertically above the pump arrangement (18).9. The pump system (2) as claimed in claim 1, characterized in that theenclosure (14) is designed with an outer perimeter that fits inside aworking aperture in a deck of a floating vessel, the vessel beingdesigned to be capable of lowering the enclosure (14) down into thewater via said working aperture in the deck of the vessel.
 10. The pumpsystem (2) as claimed in claim 1, characterized in that the enclosure(14) has a height that is greater than the largest horizontal transversedimension of the enclosure (14).
 11. The pump system (2) as claimed inclaim 1, characterized in that the enclosure (14) is connected via acabled connection (66) to a remote host device (72) for transmittingboth control signals to the control unit (48) and drive power to poweredequipment in the pump system (2).
 12. The pump system (2) as claimed inclaim 1, characterized in that said cooling arrangement (46) comprises:at least one closed flow circuit (58) containing a coolant, where theclosed flow circuit (58) is connected to the internal atmosphere of theenclosure (14) for absorbing heat therefrom, and where the closed flowcircuit (58) comprises a heat exchanger (60), which is connected to saidbody of water (4) on the outside of the enclosure (14) for removing heattransmitted from the internal atmosphere of the enclosure (14) via thecoolant of the flow circuit (58); and a means of delivery for thecoolant.
 13. The pump system (2) as claimed in claim 1, characterized inthat said cooling arrangement (46) comprises an open flow circuitcontaining a coolant, where the open flow circuit is connected to theinternal atmosphere of the enclosure (14) for absorbing heat therefrom,and wherein the open flow circuit is connected to a remote host device(72) for at least the circulation of the coolant, and for removing heattransmitted from the internal atmosphere of the enclosure (14) by meansof the coolant of the flow circuit.
 14. The pump system (2) as claimedin claim 2, characterized in that said lubrication arrangement (44)comprises: at least one closed flow circuit (52, 54) containing a fluidlubricant, where the closed flow circuit (52, 54) is connected tolubricated equipment in the pump system (2); and a means of delivery forthe fluid lubricant.
 15. The pump system (2) as claimed in claim 2,characterized in that said lubrication arrangement (44) comprises anopen flow circuit containing a fluid lubricant, where the open flowcircuit is connected to lubricated equipment in the pump system (2), andwhere the open flow circuit is connected to a remote host device (72)for at least the circulation of the fluid lubricant, and for lubricatingthe lubricated equipment in the pump system (2).
 16. The pump system (2)as claimed in claim 1, characterized in that the wall of the enclosure(14) is provided with at least one wet-mateable plug connection (64)designed for coupling to a separate, cabled connection (66) fortransmitting both control signals to the control unit (48) and drivepower to powered equipment in the pump system (2).
 17. The pump system(2) as claimed in claim 4, characterized in that said remote host device(72) is a surface installation on land or offshore.
 18. The pump system(2) as claimed in claim 1, characterized in that the enclosure (14) isflow-connected to at least one underwater installation (38) fortreatment of the injection water (10); and said underwater installation(38) is located underwater in said body of water (4).
 19. The pumpsystem (2) as claimed in claim 18, characterized in that said underwaterinstallation (38) comprises at least one arrangement for removing solidparticles from the injection water (10) without filtering.
 20. The pumpsystem (2) as claimed in claim 17, characterized in that said underwaterinstallation (38) comprises at least one arrangement for chemicaltreatment of the injection water (10).
 21. The pump system (2) asclaimed in claim 18, characterized in that said underwater installation(38) comprises at least one arrangement for the destruction of organicmaterial in the injection water (10).
 22. A method for transportinginjection water (10) to an underwater injection well (12), where themethod uses a pump system (2) comprising a pressure-tight enclosure(14), which includes: a pump arrangement (18) for pumping the injectionwater (10); a drive arrangement (20) connected to the pump arrangement(18) for operation of the latter; a cooling arrangement (46) forremoving heat from the interior of the enclosure (14); and at least onecontrol unit (48) for operating control of at least said drivearrangement (20); wherein the enclosure (14) also comprises: an inlet(24), which is flow-connected to an upstream side of the pumparrangement (18); and an outlet (28), which is flow-connected to adownstream side of the pump arrangement (18); wherein the methodcomprises the following steps: (A) lowering the pressure-tight enclosure(14) down into the water and locating the enclosure (14) underwater,characterized in that the method also comprises the following steps: (B)flow-connecting the inlet (24) of enclosure (14) to a body of water (4)in which the enclosure (14) is located, water from this body of water(4) being used as injection water (10) to said underwater injection well(12); (C) flow-connecting the outlet (28) of the enclosure (14) to theinjection well (12); and (D) starting said drive arrangement (20) andthereby the pump arrangement (18) in order thus to pump the injectionwater (10) onwards to the injection well (12).
 23. The method as claimedin claim 22, characterized in that the method also comprises thefollowing steps: aligning the pump arrangement (18) and the drivearrangement (20) vertically in relation to one another; designing theenclosure (14) with an outer perimeter that fits inside a workingaperture in a deck of a floating vessel; and lowering the enclosure (14)down into the water via the working aperture in the deck of the vessel.24. The method as claimed in claim 22, characterized in that the methodalso comprises the following steps: locating at least one underwaterinstallation (38) for treatment of the injection water (10) underwaterin said body of water (4); and flow-connecting the enclosure (14) tosaid underwater installation (38) for treatment of the injection water(10).
 25. The use of a pump system (2) as claimed in claim 21 fortransporting injection water (10) to an underwater injection well (12).26. The use of a method as claimed in claim 22 for transportinginjection water (10) to an underwater injection well (12).